Hi I was employed as a helthe physics monitor in the yard,first of all a reactor was never removed from any nuke at Chatham.all the reactors are still on board the hulks at Rosyth awaiting disposal.
It sounds to me as if the incident you refer to was removing a fuel rod to the core pond.
This entailed lifting the rod,enriched uranium,into a stainless steel container(known as the Guinness bottle) that was then lifted by the "big"crane to the core pond where the rod was removed ,under water, and placed in storage Untill being transferd to a rail flask for transport to a disposal site.
Please don't take this as a criticism,or me being a smart arse,thank you ,
Be pleased to help with any other inquiries ref refueling nuks from one who has been there. Got the t shirt,and the radiation dose to prove it